I wanted to pull this sidebar conversation out from the video interview because I've noticed the same thing. Online publications and blogs do seem to read differently; readers who are looking for specific content vs. daily or monthly readers looking for general content. For example, in the interview, Gross notes that if he writes an article about the fishing industry, he tends to get more readers from the fishing industry. It makes sense.
The point is valid, but I want to expand on it. I wonder if the same isn't really true for print publications, but we just don't notice. For example, when we co-owned and managed a concierge and hospitality trade publication called Key News * Las Vegas, subscribers tended to browse the publication and only focus in on the specific content they found worthwhile. But, I only knew that based on qualitative research. Online, it's much more apparent because of analytics.
This is interesting to me because some bloggers write about having a low number of regular readers. However, it also seems that while regular readers are valued, they might play a smaller role in the success of an online publication. And if that is true, it might make bloggers think twice about each post because the value of each post becomes more important.